ROCHESTER, Minn. - Winter months can be hard on Minnesota's deer population. 

Deep snow, frigid temperatures, and a lack of accessible food contribute to this.

Every year, the Minnesota Department of Natural Resources uses a variety of factors, called a severity index, to determine just how harsh the winter was on the white tail deer population. 

The DNR says it felt the severity index was set too high, so they lowered the threshold. 

Here's an overview of how it works. 

A severe winter is categorized as 120 or more points on the severity index. 

A point is accumulated each day when there is more than 15 inches of snow on the ground. 

Another factor taken into account is below zero temperatures. 

Every day the temperature dips below zero, one point is added to the severity index. 

Severe winters used to be 180 points and above. 

Now the threshold is 120. 

Based on what we had seen in the past, that the thresholds for severe winter were maybe set too high and that we were seeing increased mortality events, even at lower severity indexes," says Brandon Schad, the Rochester Area Wildlife Supervisor. 

He says this winter has been a pretty mild winter, but he says that could always change these next few months.